Ryazanian (Berriasian) molluscs and biostratigraphy of the Dutch and Norwegian North Sea area (south of Viking Graben)

Abstract Herein, Ryazanian (Berriasian) macrofossils from three well cores in the Central Graben (wells B18-02, L06-02, The Netherlands) and on Jæren High (well 7/7-2, Norway) southern North Sea region are described. Macrofossils mainly represented by buchiid bivalves ( Buchia volgensis ) ammonites Surites , Lynnia Praetollia ?). genus is recorded for first time outside its topotypical area, systematic position stratigraphic ranges discussed. Additionally, studied core sections yielded coleoid remains a single limid bivalve. Based of key ammonite genera Lynnia, Bojarkia ), zonation stage reconsidered. Uppermost Volgian to faunas quite consistent diverse but showing higher degree similarity throughout Panboreal Superrealm as compared those rest Upper Middle Volgian. only species known East Anglia, which strong contrast high diversity Greenland remainder Boreal Realm. We hypothesise that such differences distribution general, absence other than south particular, result anoxic bottom water conditions Viking Strait. unusually wide geographic range B. distant areas Mexico Crimea, suggests potential tolerance this adverse conditions.